1. Field of the Invention
The present invention relates to a navigation apparatus which displays a map image and the like around a position of a vehicle and a method for drawing the map.
2. Description of the Related Art
A navigation apparatus has been known in which, in order to stereoscopically display a specific background polygon representing a water area, the specific background polygon is displayed after reduction conversion with its center-of-gravity as the center, and an area between the polygon before and after the reduction conversion of the specific background polygon is displayed as a frame polygon (see, for example, Japanese Unexamined Patent Application Publication No. 2006-58530). In this navigation apparatus, a color expressing a shadow is added on the upper face of the specific background polygon and on the side face shown by the frame polygon, for drawing the specific background polygon under a light source at a predetermined position.
In the simplest method, images of buildings and the like can be moved in an oblique direction and shadows can be added thereto. In this method, however, there has been a problem in that if a water-related object having a specific shape, for example a water-related object having a shape of the sea with a narrow pier extending thereover, is moved in an oblique direction, the narrow pier would be covered by the shadow and would no longer be visible. On the other hand, in the navigation apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2006-58530, such a problem does not arise because shadow images are generated by using the shape of the sea which has been reduced; however, a reduction conversion is necessary to add shadows, which results in a complicated process.